P53 deletion is not a frequent event in multiple myeloma

Recently a high incidence of interstitial deletion of the P53 locus has bee n reported in multiple myeloma (MM) patients. Considering the importance of such an event, we analysed 79 patients with advanced-stage disease using f luorescence in situ hybridization (FISH). Strikingly, we found only 7/79 pa tients with a P53 deletion. In order to rule out any differences in probe s election, we reanalysed all the patients with the same probe as that used i n a previous study, and confirmed the low incidence of p53 deletion (7/79, 9%). The only explanation is a difference in efficiency. Since hybridizatio n is far less efficient on malignant plasma cells than on other bone marrow cells we suggest that this poor hybridization efficiency may lead to a fal se P53 deletion.